Field of the Invention
The present invention relates to a winch for a pipelayer and a pipelayer equipped with the same.
Background Information
A pipelayer is a work vehicle for laying pipes in a construction site of pipelines for transporting oil or natural gas. Many pipelayers are tractor-based vehicles, and each is equipped with a winch and a counterweight on one width directional (transverse directional) end thereof while being equipped with a boom suspended by a wire rope released and stretched from the winch on the other width directional end thereof. In a construction site of pipelines, a plurality of pipelayers are aligned, and each lifts up a pipe by causing the winch to wind up the wire rope. The winch is coupled to a hydraulic motor and is driven by means of hydraulic pressure.
To prevent occurrence of uneven winding in winding up a wire rope onto a drum in such a winch, generally employed is a method of reducing a fleet angle defined as an angle formed by a winch drum and a wire rope released and stretched from the winch drum. This is due to the following: in winding up the wire rope, a thrust directional force is generated and the wire rope tries to move from an end of the drum towards the middle of the drum; however, when the fleet angle is increased, the force is increased and the wire rope inappropriately moves; and thus, uneven winding is likely to be caused. Moreover, as a method of preventing occurrence of uneven winding, various methods are employed, including that the drum is provided with a columnar roller for restraining the wire rope on the drum surface (e.g., see Japan Laid-open Patent Application Publication No. JP-A-S64-34896).